Production of anthraquinone dyes



United States Patent 3,086,024 PRODUCTION OF ANTHRAQUINONE DYES WillyBraun, Heidelberg, and Manfred Ruske and Karl Meier, Ludwigshafen(Rhine), Germany, assignors to Badische Anilin- & Soda-FabrikAktiengesellschaft, Ludwigshafen (Rhine), Germany No Drawing. Filed Jan.13, 1961, Ser. No. 82,407 Claims priority, application Germany Jan. 15,1960 Claims. (Cl. 260-326) This invention relates to a process for theproduction of anthraquinone dyes. In particular, the invention relatesto the reaction of 1, 4-diarninoanthraquinone-2,3-dicarboxylic acidimide with 5- or '6-membered cyclic esters of carbonic acid and the sameesters of sulfurous acid, these esters being derived from1,2-dihydroxyethanes or 1,3-dihydroxypropanes which may contain avariety of substituents.

The invention furthermore provides a number of new and useful dyes ofthe formulae:

0 NH; 1| l 00 a, I u 11 shaman l l l H R, Y I 00 O NH; (1) and O NH:

R; R; l l 1 N-(CHi)u! -on n, it I; oo 0 NH: (II) in which R R and Rdenote hydrogen or alkyl containing 1 to 6 carbon atoms and in which R,may also stand for the following: halogen alkyl such as chlorallcyl,bromalkyl and iodoalkyl wherein the allryl contains 1 to 6 carbon atoms,alkoxyalkyl containing 1 to 6 carbon atoms, vinyl, phenyl andpara-tolyl, and n is 0 or 1. R R and R can be the same or differentsubstituents, with the proviso that they are not simultaneouslyhydrogen. Suitable alkyl substituents for R R and R are,

i for example, methyl, ethyl, propyl or butyl. Specific examples of Rsubstituents are methoxy, ethoxy, propoxy or butoxy or the methyl,ethyl, propyl or butyl groups which are further substituted by 1 or 2halogen such as chlorine, bromine or iodine. Other examples of R includearyl groups such as the phenyl group and substituted phenyl groups suchas the tolyl group. Beside the saturated alkyl groups, R, can also standfor unsaturated hydrocarbon groups such as the vinyl group.

Dye mixtures of compounds of the formulae:

3,086,024 Patented Apr. 16, 1963 2 and mixtures of compounds of theformulae:

oo i N--CIIz. l H.CHz.OH; on i (10 6 (H111) CHLOE;

mo and NH: i! GO cm 1 ll V orton,

( NH, OH 1110 are of special technical interest.

We have found that valuable anthraquinone dyes of high purity andimproved dyeing properties are obtained by reacting1,4-diaminoanthraquinone-2,3 dicarboxylic acid imide with 5- or6-membered cyclic esters of carbonic acid or sulfurous acid; the cyclicesters are essentially derived from 1,2-dihydroxyethanes or1,3-dihydroxypropanes in which the carbon atoms may be substituted.

The cyclic esters of carbonic acid or sulfurous acidalso referred tobriefly as carbonates or sulfites-may contain as substituents forexample halogen atoms, such as chlorine, bromine or iodine atoms, alkylradicals, such as low molecular weight saturated or unsaturated alkylradicals containing 1 to 6 carbon atoms, alkoxyl groups, such as alkoxylgroups containing 1 to 6 carbon atoms or aromatic radicals, such as arylradicals with one to two benzene rings. The following compounds may begiven as specific examples: ethylene sulfite, ethylene carbonate,propylene-carbonate-( 1,2), 3-chlorpropylene carbonate- (l,2),3-methoxy-propy1ene-carbonate-( 1,2), vinylethylene carbonate,butylene-carbonate-(1,2), butylene carbonate-(2,3), phenylethylenecarbonate, 5,5-dimethy1-1, 3 dioxanone-(Z), 5-methyl-S-normal-propyl 1,3dioxanone-(Z), 5,5-dimethyl-1,3-dioxathione-(2) and 4-normal-propyl-S,5-dimethyl-l,3-dioxanone-(2 These cyclic compounds correspond to one ofthe general formulae:

II E and l R: (IV) in which E denotes a carbon atom or a sulfur atom.Each of the radicals R and R which may be alike or difierent stands fora hydrogen atom or an alkyl radical containing 1 to 6 carbon atoms, forexample a saturated radical such as methyl, ethyl, propyl or butylradical. R denotes a hydrogen atom or an alkyl or alkylene radicalcontaining 1 to 6 carbon atoms, for example a saturated or unsaturatedradical such as methyl, ethyl, propyl, butyl or vinyl. R further standsfor alkoxy-alkyl radicals containing 1 to 6 carbon atoms such asmethoxyalkyl or ethoxyalkyl, or a halogen alkyl radical containing 1 to6 carbon atoms such as chloralkyl, bromalkyl and iodine alkyl or an arylradical, for example phenyl or paratolyl radical.

Mixtures of two or more of the cyclic esters of carbonic acid and/ orsulfurous acid may also be used as starting materials for the processaccording to this invention.

For each mol of 1,4-diaminoanthraquinone-2,3-dicar boxylie acid imide,it is preferable according to the new process to start from 2 to 10mols, especially 3 to 5 mols of the cyclic esters of carbonic acid orsulfurous acid and to work in a polar organic solvent which is inertunder the reaction conditions, Le. a solvent which does not react withthe compounds to be interacted. Suitable solvents are, for example,N,N-dimethylformamide, acetamide, N-methylpyrrolidone or mixtures of thesame. It is also preferable to carry out the reaction in the presence ofabout 0.05 to 1 mol of one or more agents having a strongly alkalinereaction, as for example an alkali metal hydroxide, carbonate oralcoholate, for example of sodium or potassium. The reaction proceeds asa rule at temperatures between 80 and 180 C., advantageously between 100and 160 C., and in general does not require more than 1 to 4 hours. Withethylene carbonate, the reaction is ended after an hour. Heating forlonger periods is however not injurious.

The process according to the invention may be carried out in solventsother than the above-mentioned polar solvents, for example in the estersof carbonic acid or sulfurous acid used as reactants themselves or inthe usual organic solvents, such as nitrobenzene, ortho-dichlorbenzeneor the mixture of the three isomeric trichlorbenzenes, in the presenceor in the absence of the abovementioned agents having a stronglyalkaline action.

As a rule the reaction proceeds without difiiculty under atmosphericpressure so that in general it is not necessary to use increased orreduced pressure. When using esters of sulfurous acid as initialmaterials it is advisable to remove the sulfur dioxide formed in thereaction with the aid of a stream of gas or air led through the reactionmixture.

From the literature, for example U.S. patent specification No.2,628,963, it is already known that 1,4-diaminoanthraquinone 2,3dicarboxylic acid-(2-hydroxyethyl)- imide is obtained whenZ-hydroxyethylamine is allowed to act at 190 C. and under increasedpressure for 4 hours on l,4-diaminoanthraquinone-2,3-dicarboxylic acidirnide. The blue dye thus obtained is however contaminated by redcolored byproducts by reason of the high reaction temperature requiredfor its formation. According to the new process, however, the same dyeis obtained in larger yields and higher purity by reacting1,4-diaminoanthraquinone-2,3-dicarboxylic acid imide in a polar solventat atmospheric pressure with ethylene carbonate in the presence of anagent having a strongly alkaline reaction at 100 to 130 C., even withinan hour. The dye prepared according to the new process is superior tothe dye obtained in the known way in the clarity of its blue dyeings onfabric of polyethylene terephthalate and by its greater thermalstability.

The new dyes obtainable according to this invention, for example thecondensation products of 1,4-diaminoanthraquinone-Z,B-dicarboxylic acidimide with propylenecarbonate-( 1,2) or 3-methoxypropylene-carbonate-(1,2), vinylethylene carbonate, butylene-carbonate-(l,2),butylone-carbonate (2,3), phenyletnylene carbonate,5,5-dimethyl-1,3-dioxanone-(2), S-methyl-S-normal-propyl-1,3-dioxanone-(2) and/or 5,5-dimethyl-1,3-dioxathione-(2) are superior to1,4-diaminoanthraquinone-2,3-dicarboxylic acid-(Z-hydroxyethyl)-imideand the other dyes specified in U.S. patent specification No. 2,628,963by their brilliance and their better absorptivity. They are moreoversuperior to the dyes known from U.S. patent specification No. 2,753,356in their thermal stability, especially in fastness to sublimation andthermofixation (at 20 seconds heating at 190 C.). They are suitable asdispersion dyes quite generally for dyeing and printing hydrophobicfibrous material. Especially strong dyeings and prints are obtainedhowever on materials, such as foils, films and textile materials, forexample fibers, threads, flocks, woven fabrics and knitted fabrics oflinear polyesters, such as polyethylene glycol terep-hthalate or basedon terephthalic acid and paradimethylol-cyclohexane, which are dyed deepblue to turquoise shades of excellent light, wet and thermofixationfastness.

The invention is illustrated but not limited by the following examples.The parts and percentages are units by weight.

Example 1 16 parts of ethylene carbonate are introduced into a mixture,heated to C., of 124 parts of 1,4-diaminoanthraquinone-Z,3-dicarboxylicacid imide, 0.8 part of sodium hydroxide (finely ground) and 51 parts ofN- nlethylpyrrolidone, the mixture heated to C. within an hour and keptat this temperature for about 5 minutes. The reaction mixture is thencooled to 50 C., stirred with 100 parts of methanol, the depositedmaterial filtered off by suction at 20 to 25 C., Washed with a littlemethanol and then with water and dried. About 12.9 parts (92% of thetheory) of pure 1,4-diaminoanthraquinone-2,3-dicarboxylicacid-(2-hydroxyethyl) imide of the melting point 286 C. to 287 C. areobtained. The dye contains about 12.1% of nitrogen and dyes polyethyleneglycol terephthalate fibers greenish blue shades. The shade of color ispurer than a comparative dyeing obtained with a dye prepared accordingto Example 8 of the U.S. patent specification No. 2,628,963.

Example 2 6.2 parts of 1,4-diaminoanthraquinone-2,3-dicarboxy1ie acidimide, 1.1 parts of sodium carbonate and 23 parts ofN,N-dimethylformamide are heated together to 100 C. and stirred with 8.2parts of ethylene carbonate. The temperature is then raised within anhour to 120 C. Then the mixture is cooled to 20 to 25 C. and thereaction product filtered off by suction, washed with water and dried.The yield of l,4-diaminoanthraquinone-2,3- dicarboxylicacid-(Z-hydroxyethyl)-imide is about 92 to 93% of the theory. The dyecorresponds in its tinctorial properties with the dye prepared accordingto Example 1.

Example 3 35.2 parts of ethylene carbonate are introduced at C. into amixture of 125 parts of nitrobenzene, 31 parts of1,4-diaminoanthraquinone-2,3-dicarboxylic acid imide and 3 parts ofsodium carbonate. The whole is heated within an hour to 160 C. andstirred for 3 hours at this temperature. After cooling to 30 C., thereaction material is filtered oil by suction, washed with nitrobenzene,methanol and water and dried. About 33.8 parts (95.5% of the theory) ofdye are obtained. The dye contains about 61.1% of carbon, 4.1% ofhydrogen, 11.7% of nitrogen and 22.9% of oxygen and corresponds in itstinctorial properties to the dye obtained according to Example 1.

Orthodichlorbenzene or a commercial mixture of the three isomerictrichlorbenzenes may be used as solvent instead of nitrobenzene.

Example 4 18.6 parts of 1,4-diaminoanthraquinone-2,3-dicarboxylic acidimide and 1.8 parts of sodium carbonate are heated in 75 parts ofN-methylpyrrolidone at C. for about 10 minutes and then cooled to 100 C.At this temperature, 31.2 parts of propylene-carbonate-(l,2) areintroduced, heated within an hour to 120 C. and the mixture kept at 120C. for 2 hours. Then it is cooled to 20 to 25 C., the reaction materialfiltered 01? and washed with water. The condensation product of1,4-diaminoanthraquinone-Z,3-dicarboxylic acid imide andpropylenecarbonate-(1,2) is obtained in a yield of about 80% in the formof a dark blue powder of the melting point 263 to 265 C. The new dye,which consists of a mixture of the two compounds of the formulae:

contains about 62.4% of carbon, 4.1% of hydrogen, 11.5% of nitrogen and21.9% of oxygen and dyes polyester fabric based on ethylene glycol andterephthalic acid turquoise blue shades of very good light, wet andthermofixation fastness.

About 1.5 to 2 parts of sodium methylate or potassium ethylate may beused as the agent having a strongly alkaline reaction instead of sodiumcarbonate.

Example 5 22.8 parts of vinyl ethylene carbonate (obtainable accordingto the process of the US. patent specification No. 2,511,942) areintroduced into a mixture, heated to 70 C., of 12.4 parts of1,4-diaminoan'thraquinone-2,3-di carboxylic acid imide, 50 parts ofN-methylpyrrolidone and 1.2 parts of sodium carbonate. The reactionmaterial is then heated within an hour to 120 C. and kept at thistemperature for about 45 minutes. Then it is diluted at 20 C. with 100parts of methanol and the dye separated in the way described inExample 1. 13.5 parts of the condensation product ofl,4-diaminoanthraquinone- 2,3-dicarboxylic acid imide and vinyl ethylenecarbonate of the melting point 238 to 239 C. are thus obtained. The newdye, which consists of a mixture of the two compounds of the formulae:

N-C HLCILOH OHj dyes textile material of polyethylene glycolterephthalate brilliant turquoise blue shades of especially good colorstrength and corresponds to the empirical formula 20 15 3 5-Analysis-Calculated: C, 63.6%; H, 3.98%; N, 11.1%; 0, 21.2%. Found: C,63.09%; H, 4.35%; N, 10.99%; 0, 21.2%.

Example 6 8.2 parts of ethylene carbonate are introduced at C. into afused mixture of 30 parts of acetamide, 6.2 parts of1,4-diaminoanthraquinone-2,3-dicarboxylic acid imide and 1.1 parts ofsodium carbonate. The whole is then heated Within an hour to C., kept atthis temperature for about 20 minutes, the melt cooled to 100 C. andstirred with 90 parts of hot water. The deposited reaction material isthen filtered oif by suction at 40 C. and Washed with hot Water. The dyeis obtained in a yield of 96% of the theory. It corresponds in itsproperties with the dye obtained according to Example 1.

The same dye is obtained by working without sodium carbonate andstirring the melt for 2 hours at 160 C. instead of for about 20 minutesat 120 C.

Example 7 10 parts of 5,5-dimethyl-1,3-dioxanone-(2) are intro ducedinto a mixture, heated to C., of 25 parts of N-methylpyrrolidone, 6.2parts of 1,4diaminoanthraquinone-Z,3-dicarboxylic acid irnide and 0.6part of sodium carbonate. The mixture is then heated to C. within anhour and kept at 160 to C. for 3 to 4 hours. The reaction material isworked up as described in Example 1. The1,4-diaminoanthraquinoue-2,3-dicarboxylic acid(2,2-dimethyl3-hydroxypropyl) imide obtained in a good yield has amelting point of 239 to 243 C. The new dye of the formula:

O NH! it o o CH3 1 i N-C H:-0 H2011 i i a C 0 4) NH: (VII) dyespolyester fibers based on terephthalic acid andparadimethylolcyclohexanone powerful greenish blue shades of goodfastness properties.

The 5,5-dimethyl-l,3-dioxanone-(2) used can be prepared in the usual wayby reaction of 2,2-dimethylpropane-diol-( 1,3) with phosgene.

By using 0.8 part of potassium carbonate or 0.7 part of a mixture of 67%of sodium carbonate and 33% of potassium carbonate instead of sodiumcarbonate and proceeding otherwise as described in the first paragraphof this example, the dye of the Formula VII is also obtained in a goodyield.

Example 8 10.8 parts of ethylene sulfite are introduced into a mixtureof 6.2 parts of 1,4-diaminoanthraqumono-2,3-dicarboxylic acid imicle,1.3 parts of finely ground sodium hydroxide and 25 parts ofN-methylpyrrolidone at 140 C. The mixture is stirred for 2 hours at thistemperature; then 0.3 part of sodium hydroxide is added and stirringcontinued for another 3 hours at 140 C. Throughout the entire durationof the reaction a weak stream of nitrogen is led through the reactionmixture. The reaction material is worked up as in Example 1. 5.2 partsof the dye described in Example 1 are thus obtained.

1.5 parts of finely ground potassium hydroxide may be used instead ofsodium hydroxide.

Example 9 9.3 parts of 1,4-diaminoanthraquinone-2,3-dicarboxylic acidimide and 1 part of sodium carbonate are heated to gether in 37 parts ofN-methybpyrrolidone to 100 C. and stirred at this temperature with 7.8parts of 3-rnethoxypropylenocarbonate-(1,2) (obtainable by reaction ofB-methoxypropylene oxide with carbon dioxide). The mixture is thenheated to 120 C. and kept at this temperature for 2 hours. Then another2.6 parts of 3-methoxypropylene-carbonate-( 1,2) are added and the wholeagain stirred for 2 hours at 120 C. and then for 30 minutes at 140 C.The condensation product of 1,4-diapaaoaaaminoanthraquinone-Z,3-dicarboxylic acid imide with 3-methoxypropylene-carbonate-(1,2) is separated as described in Example 1.The yield is 7 parts. The new dye, which consists of a mixture of thetwo dyes of the contains about 10.2% of nitrogen, usually has a meltingpoint of 205 to 206 C. and dyes textile material of polyethylene glycolterephthalate deep blue shades of excellent fastness properties.

Exam ple 10 Example 11 6.2 parts of1,4-diaminoanthraquinone-Z,3-dicarboxylic acid imide and 1.1 parts ofsodium carbonate are introduced into 40 parts of fused ethylenecarbonate at 80 C. Then the melt is heated within 3 hours to 140 C. to150 C., cooled to 60 C., the melt diluted with 90 parts of water, thereaction material filtered oil by suction and Washed with warm water.the dye described in Example 1 are thus obtained.

Example 12 4.1 parts of 1,4-diaminoanthraquinone-2,3-dicarbxylic acidimidc, 18 parts of N-methylpyrrolidone and 0.4 part of sodium carbonateare stirred at 140 C. with 6.2 parts ofS-methyl-S-normal-propyl-1,3-dioxanone-(2) (obtainable by reaction of2-methyl-2-normal-propyl-propane-diol- (1,3) with phosgene) andthereafter heated to 160 C. within an hour. The mixture is kept at thistemperature for 4 to hours and the reaction material worked up in theusual way. 6.4 parts of 1,4-diaminoanthraquinone- 2,3-dicarboxylicacid-(Z-methyl-Lnormal-propyl 3 hydroxypropyl)-imide of the formula 0N112 II C O CIIa-CHz-C H1 N-CHz- GH2OII n t 0 0 N111 (VIII) and of themelting point 198 to 201 C. are obtained. The new dye contains about9.2% of nitrogen and dyes fabric on the basis of ethylene glycol andterephthalic About 6.5 parts of acid in blue shades of very good light,wet and thermoiixation fastness.

Eample 13 If 30 parts of phenyl ethylene carbonate be used in Example 4instead of proplyene carbonate and stirring is carried out for 6 hoursat 120 to 220 C., 27.2 parts of the condensation product ofl,4-diaminoanthraquinone- 2,3-dicarboxylic acid imide with phenylethylene carbonate are obtained in the form of a dark blue powder of themelting point 243 to 244 C. The new dye, which consists of a mixture ofthe two compounds of the formulae:

OK i CO 0 NH: (IXa) and 1 t iQ H CO 0111.011

0 Nth (IXb) dyes fibers of polyethylene glycol terephthalate very vlearturquoise blue shades.

Example 14 100 parts of 1,4-diaminoanthraquinone-Z,3-dicarboxylic acidimide and 9.8 parts of finely powdered sodium carbonate are heated in784 parts of N,N-dimethy1formamide for about 2 minutes at 140 C. Themixture is cooled to 100 C. and then within 5 minutes 75.8 parts of acommercial butylene carbonate mixture, consisting of about to ofbutylene-carb-onate-(1,2) and about 40 to 45% ofbutylene-carbonate-(2,3) (obtainablo by reaction of a commercial mixtureof butyleneoxide-(1,2) and butylene-oxide-(2,3) with carbon dioxide) areadded. The reaction mixture is then heated within 3 0 minutes to C.,kept for 4 to 5 hours at 120 to C. and then allowed to cool slowly to 15to 20 C. The deposited reaction material is filtered off by suction andwashed consecutively with a little N,N-dimethylformamide, methanol andwater. About 103 parts of dye of the melting point 233 to 236 C. areobtained. It dyes fabric of polyethylene glycol terephthalate turquoiseblue shades of outstanding fastness to light, thermofixation andsublimation. The new dye consists of about 40 to 50% of1,4-diaminoanthraquinone-Z,3-dicarboxylicacid-(l-methyl-2-hydroxypropyl-l)-imide of the formula:

| C o i i 'E H.011, H C 0 l 0 NH, 03 (111a) OH I! GO NH: (IIIa) NH: 11 GO onion l 1 M11 0/ CH2.CH2

O NH, Hub) and is characterized by a very good absorptivity on textilematerials of linear polyesters.

We claim:

1. A process for the production of anthraquinone dyes which comprisesreacting at a temperature of between 80 and. 180 C. about one mol of1,4-diaminoanthraquinone-2,3-dicarboxylic acid imide with about 2 tomols of a compound selected from the group consisting of the formulae:

and

in which E denotes an atom selected from the group consisting of carbonand sulfur and R R and R stand for a member selected from the groupconsisting of hydrogen, alkyl of 1 to 6 carbon atoms, alkoxyalkyl of 1to 6 carbon atoms, vinyl, phenyl, para-tolyl and chloroalkyl, bromoalkyland iodoalkyl, each of said halogen alkyls being of 1 to 6 carbon atoms,said reaction being carried out in the presence of an alkaline agentselected from the group consisting of hydroxides, carbonates andalcoholates of the metals sodium and potassium.

2. A process as claimed in claim 1 in which the reaction is carried outin the presence of an organic solvent which is inert under the reactionconditions.

3. A process for the production of anthraquinone dyes which comprisesreacting at a temperature of between 100 and 160 C. in the presence ofan alkaline agent selected from the group consisting of hydroxides,carbonates and alcohols of the metals sodium and potassium and in thepresence of a polar organic solvent which is inert under the reactionconditions about 1 mol of 1,4- diaminoanthraquinone-2,3-dicarboxylicacid imide with about 3 to 5 mols of a compound selected rom the groupconsisting of the formulae:

and

in which E denotes an atom selected from the group consisting of carbonand sulfur, R and R stand for a member selected from the groupconsisting of hydrogen and alkyl of l to 6 carbon atoms and R stands fora member selected from the group consisting of hydrogen, alkyl of 1 to 6carbon atoms, alkoxyalkyl of 1 to 6 carbon atoms, vinyl phenyl andpara-tolyl and chloralkyl, brornalkyl and iodinealkyl, each of saidhalogen alkyls being of 1 to 6 carbon atoms.

4. A composition consisting essentially of a mixture of theanthraquinone dyes of the formulae:

and

CH2.OII

CHLQCHI iVHz 5. A process as claimed in claim 3 wherein said alkalineagent is present in an amount of 0.05 to 1 moi for each mol of said1,4-diaminoanthraquinone-2,3-dicarboxylic acid.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR PRODUCTION OF ANTHRAQUINONE DYES WHICH COMPRISESREACTING AT A TTEMPERATURE OF BETWEEN 80* AND 180*C. ABOUT ONE MOL OF1,4-DIAMINOANTHRAQUINONE-2,3-DICARBOXYLIC ACID IMIDE WITH ABOUT 2 TO 10MOLS OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF THE FORMULAE:O=E<(-O-CH2-C(-R2)(-R3)-CH(-R1)-O-) AND O=E<(-O-C(-R3) (-R2)-CH(-R1)-O-)IN WHICH E DENOTES AN ATOM SELECTED FROM THE GROUP CONSISTING OF CARBONAND SULFUR AND R1, R2 AND R3 STAND FOR A MEMBER SELECTED FROM THE GROUPCONSISTING OF HYDROGEN, ALKYL OF 1 TO 6 CARBON ATOMS, ALKOXYALKYL OF 1TO 6 CARBON TOMS, VINYL, PHENYL, PARA-TOLYL AND CHLOROALKYL, BROMOALKYLAN IODOALKYL, EACH OF SAID HALOGEN ALKYLS BEING OF 1 TO 6 CARBON ATOMS,SAID REACTION BEING CARRIED OUT IN THE PRESENCE OF AN ALKALINE AGENTSELECTED FROM THE GROUP CONSISTING OF HYDROXIDES, CARBONATES ANDALCOHOLATES OF THE METALS SODIUM AND POTASSIUM.
 4. A COMPOSITIONCONSISTING ESSENTIALLY OF A MIXTURE OF THE ANTHRAQUINONE DYES OF THEFORMULAE: